This invention relates to an accurate, repeatable radial keratotomy knife. More particularly, this invention relates to a system for accurately zeroing and determining the blade extension of a radial keratotomy knife which includes an accurate linear position transducer therein. Still more particularly, this invention relates to a method and apparatus which includes a radial keratotomy knife having a linear position transducer mounted therein and connected to a circuit for accurately displaying the blade extension after zeroing. Still more particularly, this invention relates to a method and apparatus for zeroing the blade extension of the radial keratotomy knife by using a sleeve with a membrane to reflect light to a detector so that contact of the blade of the keratotomy knife with the membrane indicates a reference or datum position.
A procedure is known for the surgical correction of myopia and/or astigmatism by radial keratotomy. In this procedure, a series of radial, non-penetrating incisions are made on the periphery of the cornea, in order to alter its shape, and consequently aid in correcting the condition.
For use in such procedures, a radial keratotomy knife is known having a size and shape suitable for being held in the hand of the surgeon. Such knives include a body having a nose piece housing a footplate for receiving a blade assembly. The knife includes a structrue for advancing or retracting the blade assembly relative to the footplate to control to a high degree of accuracy the extension of the blade beyond the footplate. Such devices require visual comparison under a microscope with a predetermined physical gauge. Examples of such a knife and a gauge for determining blade extension are shown in U.S. Pat. No. 4,499,898 to Knepshield.
Such a technique is not completely advantageous because of certain inaccuracies in the technique. A major source of inaccuracy resides in the judgmental step of zeroing the blade relative to the footplate in the initial stages in order to determine the number of rotations of the knob on the handpiece to advance the blade.
Accordingly, it is an overall object of this invention to provide an improved radial keratotomy knife which has an accurate and repeatable mechanism for determining the blade extension.
It is another object of this invention to provide a keratotomy knife having a linear position transducer capable of producing an output voltage with sufficient sensitivity to display the blade extension after zeroing on the order of 1-2 microns.
It is an additional object of this invention to provide an apparatus for use with a radial keratotomy knife of the type described wherein the zeroing of the blade relative to the footplate is accurately determined to act as a reference extension for subsequent advances of the blade, while continuing to achieve the accuracy of the order indicated.
It is still another object of this invention to provide a console unit having an electronic digital readout when secured to a knife of the type described which also will receive the knife in combination with a zeroing device to establish the measuring datum when the tip of the blade is precisely in alignment with the adjacent prongs of the footplate.
It is still another object of this invention to provide a zeroing device for a knife of the type described which comprises a sterile, disposable sleeve having a membrane attached thereto for reflecting light in a system.
It is another general object of this invention to provide a console unit for receiving the knife and sleeve combination and reflecting light from the membrane in order to zero the blade extension when the footplate is in contact with the mirror-forming membrane.
These and other objects of this invention will become apparent from the following detailed written description of the invention, taken in conjunction with the accompanying drawings.